Car running poorly when cold

I have a 68 cuda with a 340. It seems to have developed a problem when it is cold. It seems to be missing and nearly stalls out. Here is the challenge.
Once it warms up it runs just fine. The choke is working correctly. I have had the same carb on when it ran Ok for me. I did change the insulating gasket but there was no change. I really think it is an electrical problem. I has electronic ignition. I recently put a chrome powermaster alternator on it.
It would be easier to figure out if it ran bad all the time.
Does anyone have a suggestions?
Thanks for the help.